1. Field of the Invention
This invention pertains to the sport of fencing, and to devices used to electronically score competition fencing.
2. Description of the Prior Art
Prior art provides no method to sense the obliqueness or the direction of the strike during fencing. Only the axial magnitude of force is detected by a calibrated spring, which is arranged to oppose the operation of an Ohmic contact electrical switch at the tip of the blade of foil or epee. The switch of prior art operates, either opening in the case of foil, or closing in the case of epee, when the required axial force is applied during the process of achieving a valid touch, or touchxc3xa9.
In recent development of the sport of fencing, a technique has arisen in which the advancing fencer whips the blade of his weapon over the shoulder of his opponent, causing the blade to bend more than 90 degrees and the tip to contact the opponent""s back with sufficient force to cause the tip sensor of prior art to register a valid touch. Since this xe2x80x9cwhip-overxe2x80x9d attack bears no relationship to useful or historical technique for either foil or epee, it is desirable to provide a sensor or electronic scoring technology able to discriminate against it.
The need for calibration of the spring in the prior art greatly complicates the maintenance, administration, and management of the weapons used in competition. Before each competition, each contestant must submit his weapon to the controlling committee to be inspected for safety and to be checked for calibration against the gravity-generated force of a standard mass. All weapons passing inspection are retained by the controlling committee and are reissued to the contestant at the time of his competition. The calibration of all weapons is again checked against a standard mass at the start of each bout. All weapons failing to pass for safety or for calibration are returned to the contestant together with a yellow or red penalty card. The contestant may then replace or repair the weapon and resubmit it to the controlling committee. Repeating this cycle of inspection and repair to adjust or replace the spring introduces delays that are not compatible with broadcast scheduling of a tournament. It is desireable to provide a scoring system that can be automatically calibrated at the start of each bout without disassembly of the weapon.
Examples of relevant prior art, all of which contain one or more of the above limitations, are U.S. Pat. No. 3,920,242 to Reith and Overman (1975), U.S. Pat. No. 4,254,951 to De Laney (1981), U.S. Pat. No. 4,892,303 to Lohre (190).
A blade tip sensor, scoring box signal input circuit, and scoring box adapter circuit are described. The sensor is comprised of a plunger, which is positioned in a cylinder with one, or optionally two elastic electrically conductive elements which sense applied force. One elastic electrically conductive element is positioned in the cylinder at the end of the plunger in such a way that principally axial force on the tip of the plunger compresses the conductive element. Optionally, a second elastic electrically conductive element is positioned near the tip of the plunger in such fashion that principally radial force acting on the tip of the plunger compresses a portion of the elastic electrically conductive element. The electrical resistance, in the circuits, which include the elastic conductive element between two rigid conductive surfaces, is reduced as compressive force increases due to the increase in area and reduction of the length of the electrical path through the elastic electrically conductive elements.
A scoring box or an adapter for scoring boxes of prior art provides circuitry to sense this change in circuit resistances of the sensor. These resistance changes produce a voltage changes in voltage divider circuits comprised of a fixed resistor and the variable resistors comprised of the elastic electrically conductive element between two rigid conductive surfaces. These voltages are either converted to digital measurements and compared to logically derived values by a digital control device, or they are compared by analog voltage comparators to voltages derived by reference voltage dividers such as potentiometers. In the case of the scoring box adapter, output circuitry of the adapter provides signals compatible with the inputs of scoring boxes of prior art.